1. Field of the Invention
The present invention relates to burner systems and more particularly to an oil burner system and control that will, when needed, provide for pumping of oil through the system in a manner to avoid going into safety lockout without overriding the safety function.
2. Description of the Prior Art
Oil burner systems for use in furnaces, boilers, water heaters etc. are well known lo in the prior art. A typical prior art system for use with an oil-fired furnace is shown in FIG. 1. In FIG. 1, an oil burner 10 is shown having a blower 12, in the lower portion thereof, and a spark igniter 14, in the upper portion thereof. A pump 16 is shown attached to the blower 12 and a supply conduit 18 connects pump 16 to a source of oil (not shown). A motor 20, which operates blower 12 to produce a stream of air, is also shown attached to pump 16. Pump 16 is operable by motor 20 to pump a fine mist of oil combined with the stream of air through blower 12 and into a combustion chamber 24 of a furnace (not shown). The spark igniter 14 employs a pair of spark electrodes 26 which, when energized, produce a spark across the gap therebetween to ignite the mist of oil and swirl the burning fuel into the combustion chamber 24 where the heat generated will be circulated to the house or other area to be heated. A flame detector such as a cad cell 28 views the combustion area to determine whether or not combustion has occurred.
A primary controller 30, which may be an R8184 manufactured by Honeywell International Inc., is shown receiving signals from a thermostat 32 over lines 34 and acts to control the operation of the oil burner 10. More particularly, when thermostat 32 sends a signal calling for more heat, primary control 30 sends a signal from terminals 40 over lines 41 to the spark igniter 14 that then operates to produce a spark across the gap between electrodes 26. Primary control 30 also sends a signal from terminals 44 over lines 45 to energize motor 20, blower 12 and pump 16 to start the mist of oil and air flowing from the blower section 12 to combustion chamber 24. If the oil and air are present and the spark ignites the oil, then the flame detector 28 provides a signal over lines 46 to terminals 47 of controller 30 to indicate that satisfactory operation has occurred. Thereafter, spark igniter 14 continues to produce a spark across the gap between electrodes 26 (referred to as xe2x80x9cintermittentxe2x80x9d operation) and the furnace produces heat until the call for heat is lost and the motor 20, the pump 16 and the igniter 14 are shut off.
The R8184 system works very nicely for substantially all normal situations that are encountered. Unfortunately, on occasions such as when the furnace is initially set up or when it undergoes extensive service, the oil lines and filter may be depleted and considerable time may elapse before air can be purged from the lines, the oil filter saturated and the oil pumped to the combustion chamber 24. Under such circumstances, when motor 20 is activated to drive blower 12 and pump 16, the spark igniter 14 produces a spark that does not ignite the oil. When the flame detector 28 does not produce a signal within a predetermined time period, (usually about 45 seconds), a safety lockout is activated which prevents further operation until the primary controller 30 is reset. A reset button 50 is provided for this purpose and after it is pushed, another delay, (sometimes as much as an additional 20 minutes) occurs before the lockout can be removed. This can be time consuming and irritating to the service technician, so many service technicians have learned that the lockout delay can be overridden by putting a jumper or short circuit across the cad cell 28. More particularly, a wire operable to produce a short circuit can be placed across terminals 47. Although this is not recommended procedure, it allows the technician to avoid the lockout which would otherwise occur after 45 seconds and the additional 20 minute delay before the lockout can be removed. Obviously, this permits more rapid maintenance but the result may be that the pump keeps pumping oil to the burners without ignition and an excess of oil may flow into the oil burner. This can be dangerous and at least requires significant and costly clean up. Furthermore, the technician may forget to remove the jumper and the control 30 will continue to believe there is flame when there is not, causing additional service requirements.
In the present invention, several features have been provided to improve the operation of the prior art. The primary distinguishing feature is the provision of a xe2x80x9cpump primingxe2x80x9d or xe2x80x9cpump purgingxe2x80x9d mode to be described below. Also, the terminals 47 to which the cad cell 28 are connected have been moved away from the rest of the terminals and placed between the primary control 30 box and the oil burner 10 surface to which primary control 30 is mounted. In this position, a jumper cannot be placed across these terminals without removing the entire primary control unit 30. Furthermore, a restricted lockout feature is provided that only allows a predetermined number of times that the system can go into lockout before the system is disabled. This feature is disclosed and claimed in our co-pending application of entitled xe2x80x9cRestricted Operating Modes for Oil Primaryxe2x80x9d Ser. No. 09/734,534, filed Dec. 11, 2000 and assigned to the assignee of the present invention. This restricted lockout feature requires something other than pushing the reset button 50 to restart the system (for example, a significant waiting period). The present invention provides a secondary override for use when the system is in restricted lockout. This may take the form of a pushing and holding of the reset button 50 for a predetermined time period (for example, 30 seconds) after which normal start up operation can resume. In any event, the side effect of slowing the service technician down occurs and, as described above, is costly from a time consumed measure and irritating to some technicians. To avoid this, the present invention provides a xe2x80x9cpump primingxe2x80x9d or xe2x80x9cpump purgexe2x80x9d feature to allow fuel oil to be pumped through the system without waiting the delay period that occurs by going into safety lockout. More particularly, a service technician, when he wishes to rapidly purge the system, can place the primary control in a xe2x80x9cpump primingxe2x80x9d mode by using a predetermined technique. For example, the reset button 50 may be pushed and released during any one of three operation states, i.e., the Valve On Delay state, the Trial For Ignition state or the Carry Over state (all of which will be described below). The xe2x80x9cpump primingxe2x80x9d mode allows the safety switch timing to be extended, for example, from 30 seconds to 4 minutes and permits enough time for the oil to be pumped through the system. In the present invention, the igniter is normally turned off after a short delay subsequent to combustion having occurred (referred to as xe2x80x9cinterruptedxe2x80x9d operation) and allows power savings, less electrode wear, less noise and longer component life. However, during xe2x80x9cpump primingxe2x80x9d operation, an air bubble could temporarily prevent oil flow, which could result in flame out. The present invention therefore provides for changing the ignition type from xe2x80x9cinterruptedxe2x80x9d to xe2x80x9cintermittentxe2x80x9d (as explained above where ignition remains on for the entire heating cycle) during xe2x80x9cpump primingxe2x80x9d operation. This increases the chance that the flame will be maintained even though an air bubble or other temporary obstruction occurs in the fuel line. These changes are effective for the current combustion cycle only, i.e., until the call for heat disappears. Thereafter, the primary control reverts to the normal safety switch timing and xe2x80x9cinterruptedxe2x80x9d ignition operation on the next call for heat. If desired, a restriction may be added to prevent an unskilled person from employing the xe2x80x9cpump purgexe2x80x9d feature. For example, the pump purge may be inhibited if the primary control has been locked out since its most recent complete heat cycle. One way of doing this is to use a counter to count the number of times that the primary control has gone into lockout and, whenever the count is not zero, it would prevent the control from going into xe2x80x9cpump primingxe2x80x9d mode. The counter could be zeroed by techniques known only to service technicians such as pushing and holding the reset button for an extended period (e.g., 30 seconds) or pushing the reset button a predetermined number of times.
Other changes include 1) connecting a valve in the oil line 18 to allow independent control of oil flow by the primary controller, 2) preventing the valve from being turned on until the igniter 14 and the motor 20 have been activated; 3) the provision of a remote alarm which allows the system to be connected to the security system to provide an alert when the system is locked out; and 4) the provision of an indicator, such as an LED light, which is programmed to provide various information at various stages of operation by, not only its on or off condition, but by flashing at various rates.